Hydroxyl radical generation theory: a possible explanation of unexplained actions of mammalian catalase.

Catalase is well known antioxidant enzyme which catalyses the dissociation of hydrogen peroxide directly into H(2)O and O(2). Mammalian catalase has been considered as 'a venerable enzyme with new mysteries'. Some aspects of its mechanism of action are mystifying and many of new findings are still unexplained. To fill up the gap we propose the 'Hydroxyl Radical Generation Theory (HRGT)' with possible mechanism. According to HRGT, mammalian catalase apart from its known catalytic reaction generates hydroxyl radicals (HRs). The HR generation mainly depends on concentration of specific substrate, hydrogen peroxide. The present theory is supported by previous experimental findings and has great deal of observational evidences. The proposed mechanism of generation of HRs answer several unexplained features of mammalian catalase, however, should be tested further.

Enhanced nitrosative and oxidative stress with decreased total antioxidant capacity in patients with oral precancer and oral squamous cell carcinoma.

OBJECTIVE: Interaction between reactive oxygen species (ROS) and reactive nitrogen species (RNS) is a crucial determinant in the etiology of oral squamous cell carcinoma (OSCC), and antioxidants protect against cellular and molecular damage caused by these. This study aims to evaluate ROS and RNS, together with the total antioxidant capacity (TAC), in serum and tissues of OSCC patients. METHOD: Total nitric oxide (TNO), malondialdehyde (MDA), and TAC were evaluated using a UV visible spectrophotometer in the serum of 30 controls, 30 precancer and 30 OSCC patients and in tissues of 10 controls and 30 OSCC patients. RESULTS: MDA and TNO were significantly elevated with concomitant depletion of TAC in serum and tissues of OSCC patients when compared to controls. A significant positive correlation (p = 0.01), at different levels between TNO and MDA in OSCC patients, was found, which increased with the grade of OSCC. CONCLUSION: An increase in the levels of TNO, NO-mediated lipid peroxidation, resulting in an increase in MDA levels, the positive TNO-MDA correlation with a deranged antioxidant defense system as demonstrated by significantly low levels of TAC; when all these facts are taken together, we can conjecture that oxidative DNA damage, a vital phenomenon for carcinogenesis, occurs due to the interplay of ROS, RNS and TAC.

Human catalase: looking for complete identity.

Catalases are well studied enzymes that play critical roles in protecting cells against the toxic effects of hydrogen peroxide. The ubiquity of the enzyme and the availability of substrates made heme catalases the focus of many biochemical and molecular biology studies over 100 years. In human, this has been implicated in various physiological and pathological conditions. Advancement in proteomics revealed many of novel and previously unknown features of this mysterious enzyme, but some functional aspects are yet to be explained. Along with discussion on future research area, this mini-review compile the information available on the structure, function and mechanism of action of human catalase.

Estimation of serum malondialdehyde in oral cancer and precancer and its association with healthy individuals, gender, alcohol, and tobacco abuse.

BACKGROUND: Tobacco and alcohol induces generation of free radicals and reactive oxygen species, which are responsible for high rate of lipid peroxidation. Malondialdehyde is the most widely used marker of lipid peroxidation. The aim of the study was to estimate serum malondialdehyde level in oral precancer, oral cancer, and normal individuals. MATERIALS AND METHODS: In this study serum malondialdehyde was measured according to the method of Ohkawa et al in 30 normal individuals and 30 patients each with histopathologically diagnosed oral precancer, and oral cancer. RESULTS: The mean serum malondialdehyde level in the control group was found to be 5.107 ± 2.32 ηmol/ml, whereas it was 9.33 ± 4.89 ηmol/ml and 14.34 ± 1.43 ηmol/ml in oral precancer and oral cancer, respectively. There was statistically significant increase in serum malondialdehyde levels in the oral precancer and oral cancer patients compared with the control group. CONCLUSION: Increased serum malondialdehyde in oral cancer and oral precancer would serve as a valuable marker for both preventive and clinical intervention, and may deserve further investigation for the early diagnosis, treatment, and prognosis.

Estimation of plasma haemoglobin by a modified kinetic method using o-tolidine.

Measurement of plasma hemoglobin is useful in variety of clinical conditions. In the present study we have developed a kinetic method to estimate plasma haemoglobin by using o-tolidine. This method is sensitive, rapid, economical, simple and less influenced by interfering substances. It measures plasma haemoglobin in the range of 6 to 400 mg/L (normal range < 50 mg/L) in less than two minutes and can be easily automated.

Development of a rapid and inexpensive plasma glucose estimation by two-point kinetic method based on glucose oxidase-peroxidase enzymes.

A rapid and inexpensive plasma glucose estimation by two-point kinetic method based on glucose oxidase and peroxidase enzymes has been developed it takes only 11/2 minutes of time and validity of the method has been discussed.